The farm machine is the driving force for various mechanization operations, which is the most important power machine in agricultural production operations. The farm machine(s) can complete most work in fields together with attached, suspended, or towed agricultural implements. The farm machine(s) can also haul a trailer to perform transportation operations. With the continuous development of agricultural labor productivity, it is an inevitable tendency that agricultural tractors develop to larger scale. This tendency is of particular note in North America and Western Europe. In Northeast China and Xinjiang Province of China, there has been a sound momentum of development in recent years. As a result, users are becoming more and more dependent on high-power tractors in the agricultural production process, so it is particularly urgent to improve the utilization rate of the tractors at work. However, when the machine components of a tractor is operating in a relatively harsh environment, the operation conditions are complicated and changeable, and the workmanship of the operators is of varying level, which leads to a low operation precision and a low land utilization rate. Also, the fuel efficiency and production efficiency of the tractor in the operation process cannot be guaranteed. Therefore, the driving of farm machines, especially large-scale farm machines, has become a key issue urgently needing to be solved in precision farming. The most effective solution to this problem is GNSS navigation automatic drive technology.
The GNSS navigation automatic drive control system mainly consists of two major components: the integrated navigation algorithm and the control algorithm. The integrated navigation algorithm provides an accurate position and attitude data for the control algorithm. The deviation value is calculated in real time by the route planning algorithm based on the position and information. Then, the deviation value is converted into a control quantity of the actuator by the control algorithm, so as to control the tractor to travel according to the planned route. In these algorithms, a kinematic model of the vehicle should be established, and the rotation angle of the front wheel in the kinematic model is one of the most important parameters of the model. Due to the installation error and manufacturing error, unstable errors will occur in the model calculation. As a result, the control algorithm is inaccurate. Even worse, the control may be divergent, such that the intention of automatic drive cannot be realized.